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Re: Discussion about "place pitch" concept

List members-

The following is an excerpt from a commentary by Shihab Shamma in last
month's PNAS dealing with the ongoing 'passionate debates between the
proponents of two very different theories of pitch':

"In recent decades, physiological investigations in humans and animals
have attempted to locate and understand the biological substrate
underlying pitch perception at various levels of the auditory nervous
system. However, despite all efforts, a deep understanding of the
mechanisms that give rise to the pitch percept remains elusive. This
uncertainty has generated passionate debates between the proponents of
two very different theories of pitch, one based on the place or location
of neural activation patterns, and the other on their temporal
modulations. This state of affairs is now likely to change dramatically
in favor of the place theories with the publication of results of
intricately designed psychoacoustic experiments by Oxenham et al. (1)
reported in this issue of PNAS. "

The article in question (a must read!):

Correct tonotopic representation is necessary for complex pitch perception.

Oxenham AJ, Bernstein JG, Penagos H.
Proc Natl Acad Sci U S A. 2004 Feb 3;101(5):1421-5.

The ability to extract a pitch from complex harmonic sounds, such as
human speech, animal vocalizations, and musical instruments, is a
fundamental attribute of hearing. Some theories of pitch rely on the
frequency-to-place mapping, or tonotopy, in the inner ear (cochlea), but
most current models are based solely on the relative timing of spikes in
the auditory nerve. So far, it has proved to be difficult to distinguish
between these two possible representations, primarily because temporal
and place information usually covary in the cochlea. In this study,
"transposed stimuli" were used to dissociate temporal from place
information. By presenting the temporal information of low-frequency
sinusoids to locations in the cochlea tuned to high frequencies, we
found that human subjects displayed poor pitch perception for single
tones. More importantly, none of the subjects was able to extract the
fundamental frequency from multiple low-frequency harmonics presented to
high-frequency regions of the cochlea. The experiments demonstrate that
tonotopic representation is crucial to complex pitch perception and
provide a new tool in the search for the neural basis of pitch.


Tony Miller
Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary
243 Charles St, Boston, MA 02114
ajmiller@mit.edu | (617) 510-3629 | http://tonymiller.info